The invention relates to a shutoff device for shutting off conduits, said device comprising a device housing having a passage, and a device movable within said housing.
Shutoff devices serve for shutting off fluid-carrying conduits. The fluids may be gases, liquids, solids and in particular multiphase systems where e.g. solids are transported together with a gaseous or liquid carrier medium. All these materials have a wide spectrum. For example, solids ranging from granular and abrasive products to logs or stones may be transported through the conduit. The liquids and gases may be aggressive substances, e.g. an acid or any type of waste water. Further, the sizes of shutoff devices may vary within a wide range. A characteristic dimension is the diameter of the passage and/or the adjacent conduits. Frequently, the diameter has a size of approximately 40 cm.
In the device housing of a shutoff device the device is linearly movable in a guideway to be moved from the open position into the closed position. This adjustment is normally effected pneumatically or hydraulically or by means of a motor. In each of these two positions the device must be sealed towards the passage to prevent the medium from uncontrolledly escaping at the shutoff device. Normally, the device is sealed by means of annular soft seals. These seals are made of graphite, PTFE filled with graphite (Manoy) or electrocoal. Such seals are rapidly destroyed by problematic media, i.e. by mechanical action, such as abrasion, or chemical or thermal action. Although the seals are arranged at a distance to the circumference of the passage they are exposed to the medium.
For improving the seals, shutoff devices have been developed which are provided with fluid cylinders in the device housing, said fluid cylinders including annular sealing bodies. Each sealing body is provided with a soft seal at the surface facing the device, said soft seal pressing against the device. This is designed to compensate for any wear of the soft seals, and it is ensured that the annular pistons are always pressed with an adequate pressure force against the device.